DE2833765A1 - METHOD AND DEVICE FOR FLUSHING THE PROCESSING ZONE DURING EDM CUTTING WITH UNDISTURBED FLUSHING CURRENT - Google Patents

Description

PATEtMTANWKUi DIETRICH LEWINiRY SliNzaoACHiMHUWW 28 33765 RCIKtR PRIfiTSCH .3. MONKS N 2 1 -1.Aig.W6

A. G. for industrial electronics AGIE Losone b. Locarno Losone / Switzerland

Method and device for flushing the machining zone during electrical discharge machining with undisturbed flushing flow

Priority: Swiss patent application no. IH36 / 78 dated April 18, 1978

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PROCEDURE AND DEVICE FOR FLUSHING THE WORK ZONE DURING SPARK EROSIVE CUTTING WITH UNDISTURBED FLUSH CURRENT

In the process of spark-erosion cutting with a wire electrode , as described, for example, in No. 13 of the Technischen Rundschau of April 3, 1970, page 9 """13 (Hallwag-Verlag Bern), the processing zone is, for example, similar to spark erosion countersinking Working medium (dielectric) is immersed or working medium is fed laterally to the processing zone with the help of rinsing jets. According to general understanding, this working medium serves to geometrically narrow the electrical channel of the individual discharges both longitudinally and transversely and thereby increase the erosion efficiency of the sparks. At the same time, the working medium is used to remove the generated abrasive particles · and the resulting gases »

The object of the invention described below is to to improve the flushing process in order to be more controllable it of the machining process and, at the same time, an increase in machining speed.

chen. In systems that carry out electrical discharge cutting in the bathroom, there is always the difficulty of having dielectric with controlled conductivity properties in the relatively small processing zone. By adding gas and abrasive particles from the machining process, the medium conductivity is always changed very quickly. Since these physical parameters have an effect on the machining gap width via the ignitability and thus ultimately on the precision of the machined workpiece, it is necessary to control the flushing state in the machining zone for precise machining. This need has led to the introduction of the jet irrigation already mentioned. Such a method with lateral flushing channels in connection with the guide means for the wire electrode is described in Swiss patent specification 526 365 (British patent specification 776 172). In the Swiss patent specification 560 574 (British patent 1475 725 or US patent 3,928,163) another design of the rinsing jet process is described by so-called coaxial jacket rinsing around the wire electrode, with which the rinsing conditions in the processing zone can be further improved. All of the described methods of processing in the bath, simple flushing of the processing zone, targeted flushing of the processing zone and finally coaxially targeted flushing of the processing zone have in common the deficiency that the zone is either insufficiently flushed as in the first-mentioned method or that through the use of several rinsing jets according to the above-mentioned method, mutual interference occurs in the processing zone due to the rinsing jets colliding from different directions. Above all , it is not possible to use the resulting gases and the

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To master the removal of particularly high workpieces inside. On the one hand, this is due to the fact that the rinsing jets can trigger a congestion through their counter-beam effect and also because of the resulting Gases and the admixed abrasion particles in the very narrow slits have no control over the conductance state more to be given. It can also happen that by joining two rinsing jets from different directions turbulence and flow accelerations also result in negative pressure areas, which give the gas a particularly high expansion capacity,

The invention is based on the object of eliminating these difficulties in controlling the flush by that the processing zone between the wire electrode and the workpiece is only controlled in one uniform direction is flowed through and that with it a safer and faster exchange of the flushing medium and a clear one Removal of the gases and abrasive particles can be guaranteed. According to the invention, this object is achieved by a flushing flow is only supplied from one side of the workpiece and thus to the processing zone by mechanical means is brought so that it flows in the cut workpiece only from the bottom to the top or vice versa. Details of the invention are described using a few examples of solutions in the following figures. Show in detail:

Fig. 1: Flushing arrangement with a pair of workpieces, each with a processing zone flushed through in one direction.

Fig. 2: Flushing arrangement with two or more pairs of workpieces

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with each in one direction d ^ rchsjpühlt'si- Bserbei management zone.

Fig. 3s rinsing arrangement for a single piece on one side Spülkananer with in one direction durchjülter Editing zone,

Fig. 4s flushing arrangement with a single jerk piece vjiü egg-side flushing chamber and mutual pressure chamber.

The illustration in FIG. 1 shows the agile wire electrode (1) for the process, which is guided on wire guide heads {2} in a geometrically defined position and generally under tensile stress. A description of the details of the design for such guide heads {2} is contained, for example, in CH patent 594 477 (corresponding to OS-P-SN 791,055 / 77). Instead of wire electrodes, bass electrodes can also be used here. The wire guide heads are connected to the structure of a machine tool via the holding arms (3). The workpieces (4) are clamped on the table of this machine tool, which is not indicated in the sketch and which executes the coordinate movements necessary for machining, generally controlled by a numerical control device. Not from one of them either. The spark generator shown in the drawing is supplied to the machining zone between the workpieces (4) and the wire electrode (I) oils and electrical machining pulses. The two workpieces (4) are now clamped together on the machine tool and kept at a distance by a sealing ring (5), which must not overlap with the machining geometry. This creates an inner washing area between the two workpieces (4), into which a washing

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connection (6) controlled with a tap (10) in the direction (7) of the working medium is flushed in. Due to the additional pressure the medium then takes its way to the exit direction (8), through the processing zone (9) between Wire electrode (1) and workpiece (4) through. It is important that, due to the arrangement, this processing zone is only flushed through in one clear direction of flow will.

It is of course easily possible to have one on each side instead of the compact workpieces (4) shown Clamping a package of individual sheets, which in practice is very often done in the manufacture of prototype parts will. To use the flushing method described, it is also not necessary for the workpieces (4) to both sides of the inner wash cabinet have the same thickness. The procedure can also be used without further ado, if on the one hand only a very thin sheet is used, this may also be used after the end of the processing does not have to have a technical purpose, so only on a real workpiece is arranged on one side of the inner washing chamber.

In terms of process technology, it is also possible without further ado that Reverse flushing directions (7) and (8), e.g. by sucking on the tap (10) instead of flushing with pressure. In practice it is however, it is much more difficult to implement such a reversed flushing direction.

In Fig. 1, the workpieces (4) and the sealing ring (5) are drawn in section, which is indicated by the hatching . The wire electrode (1) has already cut a certain slot (9) in the workpiece that is not on the

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hatched area can be seen. In the practical The application of the process naturally becomes an ever greater alternative, depending on the length of the cut created for the rinsing medium from the inner rinsing chamber. If this leak becomes so large in the case of very large machining geometries that the flushing of the machining zone would be impaired, the surgeon can easily open the already cut slot (9) in a Short interruption in processing by gluing on both sides, e.g. with metal sheets or with electrically non-conductive ones Materials, reseal.

In Fig. 2, an arrangement that is basically the same as in Fig. 1 is selected, only the wire guide heads (2) are on the holding arms (3) set to a greater distance, so that a multiple arrangement of workpiece pairs on the workpiece table (4) can be clamped. A spacer (11) must be used to ensure that between each Couple the flushing streams (8) can freely exit through a spacer space.

In Fig. 3 an arrangement is shown in which instead of the paired workpieces according to FIGS. 1 and 2 only one Single workpiece (4) is attached to the machine clamping table. The effect of a one-way irrigation is used This arrangement is obtained by the fact that a rinsing chamber (12) is attached to a Holding arm (3) is attached, which forms a wash space under the workpiece (4). This wash cabinet is opposite the Workpiece (4) still closed by a sealing membrane (13). Such a sealing membrane can also be dispensed with when the distance between the rinsing chamber (12) is opposite

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maintained over the workpiece (4) with such a small gap can be that this results in only an insignificant leakage. The rinsing chamber (12) itself has itself a flushing connection (6) through which the flushing medium is supplied in the flushing-in direction (7), controlled by the tap (10) is to leave the workpiece through the cut slot (9) in the outflow direction (8). To make things easier the introduction of the wire electrode (1) into the rinsing chamber (12) a threading slope (14) is provided, which in a possible opens into a narrow through-hole, the length of which is designed so that only a small amount of liquid leakage occurs can.

An advantage of the arrangement of a rinsing timer according to FIG. 3 over the solutions with an inner washing chamber according to FIGS. 1 and 2 consists in that the diameter of the washing arrangement is limited can remain and thus the water consumption is kept lower. The one cut by the spark erosion The slot (9) does not have to remain inside the connection area of the sealing membrane (13). If by the already cut slot (9), which gets outside the connection zone of the sealing membrane, a leak that is too large occurs, Water consumption and flushing efficiency can be improved by removing the already completed slot is closed again with a sealing material in the event of a brief interruption in operation. This sealing material can serve both to fasten the inner part that would otherwise fall out with a closed contour and at the same time also establish the electrically conductive connection to this inner part. The design of the wash cabinet and the choice of the geometric position of the flushing connection (6) is made so that the flushing flow into the slot (9) as possible turbulence-free and coaxial to the wire tool electrical

de (1) takes place. In this way it is also ensured that the flushing flow is primarily in the processing zone applies between workpiece (4) and wire tool electrode (1) and not in the slot that has already been cut (9) escapes too quickly.

In accordance with the requirements for the feed described in the Swiss patent application 594 977 already cited the generator connections to the wire electrode (1) and to the workpiece (4), the rinsing chamber arrangement can in particular with their sealing membrane (13) are designed at the same time so that these tasks of the electrical connection be accomplished with the same facility.

In Fig. 4, the construction is according to the descriptions of Fig. 3 is supplemented by a counter-pressure chamber (15), which is arranged on the opposite side to the washing chamber (12) and is also attached to a holding arm (3). As with the rinsing chamber (12), the rinsing area becomes the counter-pressure chamber (15) with respect to the workpiece (4) closed with a sealing membrane (13). The exit of the flushing flow (8) from the slot (9) must now make its way through the outlet connection (16), a throttle valve (17), to a Take the flushing medium return (18). The counterpressure chamber (15) in turn has a threading slope for the wire electrode to pass through (19), which opens into a narrow hole, through which the escape of detergent is prevented as much as possible.

By using a counter-pressure chamber (15), a pressure level can be maintained in the area of the slot (9) that the gas bubbles created by the decomposition of the working medium assume the smallest possible volume and thus disturb the processing as little as possible.

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In accordance with the objectives of the cited Swiss Patent specification 594 4 77 can perform the tasks of guiding the wire with the wire guide heads (2) are fully integrated into the flushing chamber arrangement. In addition to the various, already Advantages discussed in the discussion of the individual figures can then be in the most detailed version according to FIG Facility are obtained in which, except for minor leaks, the supply and disposal of the working medium are carried out in a completely controlled manner, in which the Guide means can be arranged very close to the processing point according to the requirements and where the Supply of the electric current also with high frequencies without disturbing induction fields coaxially to the wire can be solved.

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Claims (9)

Patent claims: Process for flushing the machining zone during electrical discharge machining Cutting workpieces with a wire or bend-shaped electrode, characterized in that the rinsing medium is supplied through a rinsing chamber on one side of the workpiece and the processing zone in one Direction controllable with flushing medium flowing through. 2. Device for electrical discharge machining according to claim 1 characterized in that by clamping two workpieces or one workpiece and an additional sheet an inner rinsing chamber is formed from which the processing zones in one direction are flowed through. 3. Device according to claim 2, characterized in that that several paired arrangements are set up. 4. Device according to claim 2, characterized in that the workpiece (4) in a manner known per se consists of a package of individual workpieces. 5. Device according to claim 2, characterized in that the already cut slot (9) to avoid from water loss is closed again with easily removable means. 6. Device for electrical discharge machining according to claim 1, characterized in that one side of the workpiece (4) is connected to the machine Rinsing chamber (12) is arranged, from which the machining 909843/0574 ORJGIiMAL INSPECTED zone in one direction controllable with flushing medium can be flowed through. 7. Device according to claim 6, characterized in that that the connection point to the workpiece (4) is sealed, e.g. by a sealing membrane (13). 8. Device for electrical discharge machining according to claim 1, characterized in that one side of the workpiece (4) is connected to the machine
Rinsing chamber (12) is arranged and that a counter-pressure chamber (15) is arranged on the opposite side, which
is also connected to the machine and that the supply and discharge of the flushing medium can be controlled, so that the processing zone can be flowed through in one direction at a controllable pressure level with flushing medium. 9. Device according to claim 8, characterized in that in a known manner the tasks of the geometric Wire guide and electrical power supply with control of the flow and pressure level solved in the processing zone in a device are. 909843/057 *